[Spoilers for anyone who hasn't played the game yet]
Hello, I don't know if you've played through the whole scene where it's mentioned or not, but it's directly mentioned in the game : the text will say which key to press to see and to turn off energy (I don't remember the exact keys, so do check what the text says, but for example, the text will mention that "you press w to see energy", then all you have to do is press that letter to see the energy, and the other key indicated later to turn it off). So if you just play through the game, it will be explicitly mentioned, don't worry :)